I believe they are not crossing they are building bridges by introducing these hybrid brokers for stockies and crypto traders to trade together. i think the lure of crypto being fast, efficient, anonymous, decentralized etc etc make it an ideal choice for stock traders to jump in. some want to embrace it for good and some just want to capitalize on it. but whatever the case maybe, its the next reincarnation for stock markets. there are lot of reasons for stock guys to jump in using these hybrid brokers.. to evade regulation, trade on leveraged products, ease of deposit, 24/7 trading and more for freedom